• Applied Chemistry for Engineering
• /
• v.17 no.2
• /
• pp.188-193
• /
• 2006

Synthesis of Boehmite particles were performed through the precipitation of aluminium nitrate ($Al_{3}(NO_{3})_3{\cdot}9H_{2}O$) with ammonia water ($NH_{4}OH$) by changing solution pH, mixing procedure, temperature, and feeding flux. The influence of the synthesis condition, which affected on the pH range of the Boehmite formation, particle morphology and pore property, was investigated. The Boehmite particles were formed in the reaction solution of pH 7.5~9. The particles prepared by P2jet type which maintained the pH uniformly during the precipitation resulted in homogeneous particles and pores because of the constant concentration of the reacted ion in the solution. It was resulted in the improvement of the specific surface area and pore volume of the particle at the same time. With the increasing of temperature and the decreasing of the feeding flux, it was occurred the large specific surface area and pore volume. Also it was presented the fibrillar shaped particles upper $60^{\circ}C$ of the reaction temperature. In this study, the optimal condition of the porous Boehmite was in P2jet type with $90^{\circ}C$ of reaction temperature and 2.5 mL/min of the feeding flux. At this time, the specific surface area, pore volume, and average pore size was $385.46m^2/g$, 1.0252 mL/g, 10 nm, respectively.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.29 no.4
• /
• pp.456-463
• /
• 1996

The purpose of the present study is to estimate the regional and seasonal variations of dissolved inorganic nitrogen (DIN) flux across the sediment-water interface of the inner and central areas of Hiroshima Bay from August 1994 to May 1995. In addition it compares the measured methods and estimates the effect of DIN released from sediment to the primary production of Hiroshima Bay. One method used in this study is to calculate DIN flux from a concentration gradient between sediment porewaters and the overlying water, and the other method is to measure DIN flux from the sediment-core experiment. The fluxes of $NH_{4}^{+}-N\;and\;NO_{2}^{+}\;+\;NO_{3}^{-}-N$ in the inner area were higher than those in central area, all of which showed seasonal variation. $NH_{4}^{+}-N$ flux was maximum in August, while $NO_{2}^{-}\;+\;NO_{3}^{-}-N$ flux was high in January compared with the other seasons. The calculated $NH_{4}^{+}-N\;and\;NO_{2}^{-}+NO_{3}^{-}-N$ fluxes from sediments were $18.2\~60.8\;{\mu}g-at/m^2{\cdot}hr\;and\;0.24\~18.2\;{\mu}g-at/m^2{\cdot}hr$, respectively. The measured $NH_{4}^{+}-N\;and\;NO_{2}^{-}+NO_{3}^{-}-N$ fluxes across the sediment-water interface were $2.00\~111\;{\mu}g-at/m^2{\cdot}hr\;and\;-265\~82.9\;{\mu}g-at/m^2{\cdot}hr$, respectively. The former was lower than the tatter. The calculated $NH_{4}^{+}-N$ flux showed closer relation to environmental factors (dissolved of gen in the overlying water, temperature and redox condition of the sediments) than the measured one did. On the other hand, in the case of $NO_{2}^{-}+NO_{3}^{-}-N$ flux both the calculated and the measured showed little relation to environmental factors, while they turned out to have stronger relation with their concentration in sediments. DIN released from the sediment is expected to support about $25\%\~67\%$ of the primary production in Hiroshima Bay.

• KSBB Journal
• /
• v.15 no.3
• /
• pp.285-292
• /
• 2000

Support media for yeast immobilization was prepared from a porous volcanic rock used as a moisturizer in orchid growing. The rock was broken to the size of 2-3 mm and burned at $600^{\circ}C$ in a furnace in order to remove organic materials blocking the pores or treated with HCI solution or NaOH solution to remove the inorganic dirts by dissolving. Even through both the acid and the akali solution were effective the latter was not recommendable because it broke the pore structure by dissolving the elements of the media. This media was mainly consisted of SiO2 with $Al_2O_3$ as a minor component and CaO and K2O as trace elements. It had the finely developed pores of $15-80\mu\textrm{m}$size. Yeast immobilization capacity of this media was about $5{\times108}$ cells/ml bed which is large enough to be used for the practical applications. Yeast immobilization capacities of Alumina and Cordierite were much smaller than that of silica-based media. Scanning electron micrograph of Cordierite and Alumina showed uneven surfaces and small size of pores in contrast to relatively smooth surface and large pores of silica based media which means that smooth surface and large pores are desirable for the good adsorption of microbes on the media.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.43 no.4
• /
• pp.362-372
• /
• 2010

In order to understand what leads to the appearance of harmful Chattonella algae in the Yeosu coastal waters of Korea, we measured environmental parameters every week at one station from May to November, 2006, and April to October, 2007. Four species of Chattonella appeared during the monitoring period: C. antiqua, C. globosa, C. marina and C. ovata. The range of water temperature and salinity were $15.0-27.9^{\circ}C$ and 17.6~33.0 psu, respectively, when Chattonella appeared, and their maximum cell density (4,840 cells/L) was at $27.1^{\circ}C$ and 33.0 psu. During the monitoring periods, the range of dissolved inorganic nitrogen (DIN), phosphate (DIP) and chlorophyll $\alpha$ (Chl-$\alpha$) concentrations in surface waters were $1.20-52.23\;{\mu}M$ ($8.59{\pm}8.97\;{\mu}M$), $0.03-1.56\;{\mu}M$ ($0.47{\pm}0.31\;{\mu}M$) and $0.45-31.12\;{\mu}g/L$ ($3.58{\pm}4.77\;{\mu}g/L$), respectively. Chattonella occurred at low cell density when the Chl-$\alpha$ concentration increased because of supplied nutrients, whereas their cell density increased during the periods of rapid decrease in Chl-$\alpha$. The results of growth experiments based on batch culture showed that the half saturation constant ($K_s$) of C. antiqua on ammonium (${NH_4}^-$), nitrate (${NO_3}^-$) and phosphate (${PO_4}^{2-}$) were $3.89{\mu}M$, $5.01\;{\mu}M$ and $0.63\;{\mu}M$, respectively. These Ks values are higher than those reported for diatoms and other flagellates at the DIP concentration (average $0.47{\mu}M$) of Yeosu coastal waters. Although the maximum specific growth rate (${\mu}_{max}$) of C. antiqua was lower than diatoms, it was higher than those of other flagellates. Therefore, our results indicate that the DIP level in the study area was too low to support Chattonella blooms, although Chattonella species have physiological characteristics that enable them to grow more rapidly than other flagellates when nutrient levels are higher than their $K_s$.

• Journal of the Korean Ceramic Society
• /
• v.39 no.5
• /
• pp.503-510
• /
• 2002

Silicon carbide candle filters for the pressurized fluidized bed combustion system were fabricated by extrusion process. Carbon black was added to control the porosity. Inorganic additives such as clay and calcium carbonate were added to exhibit appropriate strength. Silicon carbide layer with a finer pore size (mean pore diameter ~$10{\mu}m$) was coated on the silicon carbide support layer (mean pore diameter ~$47{\mu}m$, porosity ∼40%). After that, the filter was sintered at 1400${\circ}C$ in air. We evaluated the filtration performances of the filter at 500${\circ}C$ and $5kgf/cm^2$ of pressure. As a result, high separation efficiency, >99.999% was measured. It is expected that silicon carbide candle filter can be successfully used for the pressurized fluidized bed combustion system.

• 한국해양학회지
• /
• v.27 no.2
• /
• pp.91-100
• /
• 1992

For the study on the structure and characteristics of the primary production system in the southern waters of the East Sea, chlorophyll, phytoplankton standing stocks. nutrients and hydrographic properties were investigated and analyzed in conjunction with measurement of C-14 based primary productivity. The primary productivity was relatively high in comparison with the previous studies, ranging from 284 to 4,574 mgC$.$m/SUP -2/$.$day /SUP -1/ and averaged to be 2,000 mgC$.$m/SUP 02/$.$day/SUP -1/. The standing stocks within the euphotic zone were fairly high, but ambient inorganic nitrogenous nutrient concentrations were too low to support the high production. This implied that there might be active recycling of nitrogenous nutrients by heterotrophic processes and the upward flux of nutrients by vertical mixing. Subsurface chlorophyll maxima were continuously observed in the lower parts of the euphotic layer and the depth coincided with the nutricline rather than isopycnal surfaces, supporting the view that chlorophyll distributions and primary production were primarily influenced by nutrient supply. Despite low nutrient concentrations, phytoplankton standing stocks and production were fairly high and the fraction of autotrophic nano- and picoplankton production was significant.

• Journal of Conservation Science
• /
• v.27 no.3
• /
• pp.313-322
• /
• 2011

The floral wall of Lee Sang-beom's House and Atelier, which is No. 171 of the Registrated Cultural Heritage was conserved. In addition, materials characteristics and manufacturing technique have revealed through the scientific analysis. As a result of the analysis, samples were divided into three sections; the support layer that is made from block bricks, the paint layer and the cement mortar layer on the paint layer for the reinforcement of the construction. The higher layer lies, the finer grains it has. Furthermore, a little it was generated a small quantity of pores and calcium carbonates ($CaCO_3$) generated due to aeration of cement mortar. The patterns of letters, animals and plants pattern were expressed in the paint layer by relief and openwork. The results of qualitative analysis of the pigments of the paint layer were detected components of carbon black (C), Fe oxide ($Fe_2O_3$) and oyster shell white ($CaCO_3$, or quicklime). On the other hands, as the conservation of the floral wall, stainless frames were set up for the structural stability, the cement mortar were removed from the surface and the partly damaged and cracked areas were filled with KSE Filler A, B.

• Korean Journal of Microbiology
• /
• v.12 no.4
• /
• pp.159-179
• /
• 1974

In order to investigate morphological and cultural characteristics of strains in species, Flammulina velutipes, the author collected isolates of Flammultina velutipes at 49 locations in Korea and cultivated these isolates on the various kinds of solid media. After investigating the cultural characteristics, appeared on the various media, he obtained the following results : 1. The variation of colors in the fruit bodies is connected with the variation of climatic environments(composite effects between mean temperature in January and number of rain days of 1mm and over precipitation). The author, therfore, can find out the trend that brown type is distributed in the midland climatic region and yellow type in the southern climatic regoin. 2. Two types can be classified into several strains respectively : the strain of abundant or insufficient productivity, and strain of selectivity or non-selectivity of media. 3. According to the results of mutual comparison of soluble mycelial proteins by disc electrophoresis using polyacrylamide gels, each type has special common protein fractions(brown type : band located at 26..5mm position from surface of gel, yellow type : band located at 24.5mm position from surface of gel), and each strain has special protein fractions too. Therefore this phenomenon seems to support the results obtained by the above-stated morphological and cultural studies. 4. In the adaptability of strains to the temperature, every strain has the nature of growing in lower temperature(the optimum temperature of 20.deg.C to 25.deg.C) except that YI-1 strain has the optimum temperatue of $25^{\circ}C$-26^{\circ}C. And mycelial growth of every strain is discontinued at $35^{\circ}C.$ 5. In the adaptability of strains to the H-ion concentration, every strain has wide adaptable range of H-ion concentration, and has optimum range of pH 5.5 to 6.6 in mycelial growth excepting YA01, BI-2 and YI-1. 6. In the utility of carbon sources, the mycelial growth of every strain is very poor on the media containing xylose(average diameter of mycelial growth : 18mm), and most strains utilize favorably sucrose(39mm), maltose(37mm) and dextrose(35mm) in mycelial growth. In the utility of nitrogen sources, every strain utilizes favorably organic nitrogens(36 mm)more than inorganic nitrogens (25 mm), and utilizes fully peptone nad asparagine in organic nitrogens. Especially BA-1, BIK-2 and YA-1 strains grow vigorously on each media containing various carbon and nitrogen sources. 7. The characteristic tests of the number of days required for mycelial growth, the number of days requried for sprout of young bodies, the length of stipe and the number of fruit bodies formation seem to be useful methods in the early selection of the strain of the abundant productivity.

• The Journal of the Korea Contents Association
• /
• v.22 no.7
• /
• pp.55-62
• /
• 2022

The perovskite solar cell is an active part of research in renewable energy fields such as solar energy, wind, hydroelectric power, marine energy, bioenergy, and hydrogen energy to replace fossil fuels such as oil, coal, and natural gas, which will gradually disappear as power demand increases due to the increase in use of the Internet of Things and Virtual environments due to the 4th industrial revolution. The perovskite solar cell is a solar cell device using an organic-inorganic hybrid material having a perovskite structure, and has advantages of replacing existing silicon solar cells with high efficiency, low cost solutions, and low temperature processes. In order to optimize the light absorption layer thin film predicted by the existing empirical method, reliability must be verified through device characteristics evaluation. However, since it costs a lot to evaluate the characteristics of the light-absorbing layer thin film device, the number of tests is limited. In order to solve this problem, the development and applicability of a clear and valid model using machine learning or artificial intelligence model as an auxiliary means for optimizing the light absorption layer thin film are considered infinite. In this study, to estimate the light absorption layer thin-film optimization of perovskite solar cells, the regression models of the support vector machine's linear kernel, R.B.F kernel, polynomial kernel, and sigmoid kernel were compared to verify the accuracy difference for each kernel function.

• The Korean Journal of Food And Nutrition
• /
• v.25 no.3
• /
• pp.564-569
• /
• 2012

Selenium was initially considered toxic to humans, but it was then discovered that selenium is essential for normal life processes. Selenium plays important roles in antioxidants. It is expected that chitosan microcapsules containing nano-selenium will be able to be used as a key material in bio-medical and cosmetic applications. The high concentration of chitosan derivatives guarantees increased antioxidative activity. Both inorganic and organic forms of selenium can be nutritional sources. The antioxidant properties of selenoproteins help prevent cellular damage from free radicals. The objective of this experiment was to study the antioxidative activity of chitosan nano-selenium. Our experiments were divided into five groups, in the presence of various concentrations(0.1%, 0.3%, 0.5%, 0.7%, and 0.9%) of chitosan. We performed an assessment of the antioxidant properties and cytotoxicity of respective concentrations of chitosan nano-selenium. The antioxidant activity was examined by the free radical scavenging activity on 1,1-diphenyl-2-picrylhydrazyl(DPPH) assay. The cytotoxicity effect was measured by means of 3-(4,5-dimethylthiazole-2-yl)-2,5-diphenyltetrazolium bromide(MTT) assay. As a result, the electron donating abilities of 0.1%, 0.3%, 0.5%, 0.7%, and 0.9% of chitosan nano-selenium exhibited effective andioxidant scavenging activity at 12.5 ${\mu}g/m{\ell}$ against DPPH radicals. 0.3% chitosan nano-selenium did not show cytotoxicity on human keratinocytes. In general, the cytotoxicity of 0.1% and 0.9% chitosan nano-selenium showed the lowest effects. Though low cytotoxicity of 0.5% and 0.7% chitosan nano-selenium exhibited 29.67% and 38.4% against human keratinocytes on adding 100 ${\mu}g/m{\ell}$ and 50 ${\mu}g/m{\ell}$, respectively, cell vitality was recovered with 200 ${\mu}g/m{\ell}$. These findings support the notion that chitosan nano-selenium may be useful as a new active ingredient source for bioactive compounds.